In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention.
Rotatable drilling tools are often provided as integral tools or with replaceable or integrated cutting inserts having cutting edges, but also as a tool composed of axial parts. Such axially split tools comprise a basic body and a head that is detachably connected with the same, and thereby replaceable, and in which the cutting edges are included. In such a way, the major part of the tool can be manufactured from a comparatively inexpensive material, such as steel, while a smaller part, viz. the head, can be manufactured from a harder and more expensive material, such as cemented carbide, cermet, ceramics or the like, which gives the cutting edges good chip removing capacity, good machining precision and a long service life. In other words, the head forms a wear part, which can be discarded after wear-out, while the basic body can be re-used several times.
A drilling tool of such an axially split type is known by EP 2 266 736. In the document, a rotatable tool is disclosed, which comprises a basic body and a head that is connectable to the basic body by means of a journal projecting toward the basic body. This journal is insertable into a correspondingly formed axial recess in the end of the basic body facing the head. The head can be locked to the basic body by means of a locking screw that extends radially through the basic body and that can be brought to abut and press against a shoulder surface of the journal.
This known tool works well in many applications. However, it has turned out that there may occasionally emerge problems of cracks or in the worst case breakage in the mutually facing ends of the basic body and/or the head.